山地古建筑木结构强震破坏机理及抗震加固方法研究

Structural dynamic responses of the ancient timber structures located on the mountains differ from those located on the flat ground due to unequal heights of column bottom and irregularities in planar and vertical arrangements. It was found from previous severe earthquakes that such ancient timber structures on the slope in seismic-prone areas suffered from more significant damages than those on flat ground, while failure mechanism of these ancient timber structures on the slope still remains unclear. Based on the structural configurations and failure modes of typical ancient timber structures on the slope located in seismic-prone areas of Southwest China, this study aims to investigate the mechanical behaviors, failure positions and failure modes of such ancient timber structures with unequal heights of column bottom and unsymmetrical planar arrangements by performing large-scale test on such structural models. Based on the mechanical models of plinth, mortise and tenon connection and bucket arches, non-linear dynamic analysis of such ancient timber structures, utilizing multi-scale model construction technique, is conducted to investigate the influential parameters on structural damages and build the bridge among theoretical knowledge, experimental observations and characteristics of seismic damage. The strong earthquake-induced failure mechanism of such ancient timber structures is revealed and the damage criteria based on both the inter-story drift and energy dissipation indices is presented. The damaged structures are then strengthened by FRP, flat steel or dampers based on the characteristics of seismic damage. Damages and failure modes of these strengthened structures are reevaluated to obtain an effective retrofitting method of such ancient timber structures based on the damage-controlled concept. Findings of this study are expected to provide theoretical supports for protection of the ancient timber structures on the slope.

山地古建筑木结构具有柱底不等高约束、平面和竖向不规则等特点，导致其动力特性与平地古建筑不同。历次强震的震害表明，高烈度区山地古建筑木结构破坏程度比平地古建筑更严重，破坏特征也不同，而其破坏机理尚不明确。本项目针对我国西南高烈度区典型山地古建筑木结构的构造特点和震害特征，采用大比例模型试验，研究古建筑木结构在柱底不等高约束、平面不对称下的受力机理、破坏部位和破坏特征；基于柱础、榫卯和斗栱等力学模型，采用多尺度建模进行非线性动力全过程模拟，分析强震破坏模式的影响因素及其规律，构建理论认识、试验现象和震害特征之间的联系，揭示山地古建筑木结构强震破坏机理，建立基于层间位移和能量耗散的双参数破坏准则。根据其地震破坏部位，采用FRP、扁钢及阻尼器等方法加固，分析加固后结构的损伤程度和破坏模式，评价不同方法的加固效果，提出基于地震损伤控制的山地古建筑木结构抗震加固方法，为山地古建筑保护工程提供理论支撑。

本项目聚焦山地古建筑木结构，从材料、构件到结构的三个层面，较全面地开展了山地古建筑木结构强震破坏机理及减震加固方法的研究。在材料层面上，根据西南地区山地古建筑木结构的常见树种，开展了云杉木物理特性的试验研究。完成了21个微观形貌变形分析试验、128个单轴受压试验、18个循环受压试验、6个密度和6个含水率测试，给出了循环受压应力应变曲线的控制参数，并建立了循环受压统一本构模型。在构件层面上，开展了柱脚节点、榫卯节点及扇形粘弹性阻尼器的研究。基于在地震作用下不同的柱脚节点运动状态，建立了柱脚节点力学模型，获得了柱脚节点力学性能随木材强度、高径比和轴压比的关系。开展了12个古建筑木结构透榫节点力学性能试验，掌握了透榫节点在不同榫头长度下的破坏模式和力学性能，并基于试验结果，建立了透榫节点数值精细模型，分析了不同影响因素及其耦合对透榫节点力学性能的影响，并建立了考虑多因素影响因子的透榫节点力学模型。研发了适用于古建筑木结构榫卯节点的扇形粘弹性阻尼器，通过12个构件的拟静力试验，获得了扇形粘弹性阻尼器加固榫卯节点的损伤特征、刚度恢复、耗能能力以及榫头抗拔出能力等。在结构层面，开展了山地古建筑木结构的原位动力测试、两层足尺山地古建筑木结构的抗震性能与减震加固试验研究。对2个典型山地古建筑木结构进行了原位动力特性测试，并采用了峰值拾取法（PPM）和随机子空间法（SSI）进行了模态参数识别，提出了山地古建筑木结构的原位动力测试方法。在抗震性能中，开展了两层足尺古建筑木构架拟静力试验，对比了不等高与等高木构架的变形特征与滞回耗能能力，揭示了强震下山地古建筑木结构的破坏机理。采用研发的扇形粘弹性阻尼器加固两层足尺古建筑木构架，对比了粘弹性阻尼器对等高和不等高木结构减震性能的影响，并提出了基于位移控制的山地古建筑木结构减震加固设计方法。项目研究成果可为山地古建筑木结构的保护与修缮提供科学依据。